Controlled Flight Into Terrain (CFIT) has been identified as a major cause of helicopter accidents. This phenomenon usually occurs under degraded visual conditions, such as when flying under Visual Flight Rules (VFR) at night or during flight in Instrument Meteorological Conditions (IMC). The introduction of Ground Proximity Warning Systems (GPWS) resulted in a significant decline in the number of CFIT incidents. GPWS equipment automatically provides a warning to the flight crew when an aircraft is in potentially dangerous proximity to the ground. The Helicopter Terrain Awareness and Warning System (HTAWS) provides rotorcraft flight crews with aural and visual alerts of a pending collision of the terrain. Forward Looking Terrain Avoidance (FLTA) is a look-ahead function that provides enhanced awareness using terrain and obstacle displays. HTAWS provides warnings when the following conditions are detected, for example: excessive descent rate, excessive terrain closure rate, excessive altitude loss after take-off or go-around, unsafe terrain clearance, excessive deviation below an instrument glide path.
HTAWS's “look-ahead” mode or Enhanced Mode generally provides satisfactory alerting over land using GPS position and a terrain database. However, offshore operations, such as in support of oil and gas exploration, have shown that HTAWS is not optimized for the offshore operational environment.